HEMATITE GRAIN POWDER FOR MAGNETIC RECORDING MEDIUM USING METALLIC MAGNETIC GRAIN POWDER CONSISTING ESSENTIALLY OF IRON, NONMAGNETIC SUBSTRATE OF MAGNETIC RECORDING MEDIUM USING THE HEMATITE GRAIN POWDER, MAGNETIC RECORDING MEDIUM USING THE NONMAGNETIC SUBSTRATE AND PRODUCTION OF THE HEMATITE GRAIN POWDER

摘要

PROBLEM TO BE SOLVED: To obtain a nonmagnetic grain powder for a nonmagnetic substrate with the deterioration of the magnetic characteristic suppressed by heating an acicular goethite grain coated with an antisintering agent to densify it, wet-crushing and then heat-treating the grain. ;SOLUTION: An acicular goethite grain with the surface coated with an antisintering agent or an acicular goethite grain is heated and densified to obtain an acicular hematite grain, which is heated to 550C to obtain a densified hematite grain. A slurry contg. the densified acicular hematite grain is wet-crushed, and then the slurry is heat-treated at pH13 and 80C. The obtained grain is filtered off, washed with water and dried. Consequently, a hematite grain powder for the nonmagnetic substrate of a magnetic recording medium having 0.3m average major axis, 1.50 major axis distribution as a geometrical standard deviation and 35m²/g BET specific surface and with the soluble sodium salt content controlled to 150ppm, expressed in terms of SO₄, is obtained.;COPYRIGHT: (C)1997,JPO